This application claims the priority of 103 47 127.8 filed in Germany on Oct. 10, 2003, the disclosure of which is expressly incorporated by reference herein.
The invention relates to an actuator for a cryogenic valve having a pneumatic cylinder.
Different mechanical, electric or pneumatic actuators are known for a valve. However, the known solutions are not very suitable for actuating a cryogenic valve; that is, for actuating a valve which delivers a cryogenic medium, such as low-temperature liquefied gas.
It is therefore an object of the invention to provide an actuator for a cryogenic valve which is easy to manufacture and can be reliably operated.
This object is achieved in that the pneumatic cylinder is in an operative connection with the valve needle by way of a lever, the lever being rotatably connected on one side with a linkage.
The invention permits a spatial separation of the pneumatic system from the valve so that no cold transfer can take place from the cryogenic valve to the pneumatic parts. As a result, it is ensured that the pneumatic parts are subjected approximately to room temperature. The avoidance of the exposure of the pneumatic system to very cold temperatures prevents wear effects as a result of thermal tensions in the components and ensures a reliable operation of the pneumatic system and thus of the valve actuation. The construction of the actuator according to certain preferred embodiments of the invention requires a double-acting pneumatic cylinder which, when moving out into one direction, opens the valve and, when moving out into the other direction (moving in) closes the valve.
In certain preferred embodiments of the invention, the linkage itself is rotatably disposed. This has the advantage that, when the pneumatic cylinder is moved in and out, a small relative movement of the linkage per se is permitted and a tilting effect upon the valve is thereby prevented. While a rigid fastening of the linkage can still be tolerated during small valve movements or small angular movements of the valve, the rotatability allows larger movements.
In certain preferred embodiments of the invention, the lever can be connected with a spring. The spring can preferably be fastened to the other side of the lever—thus, opposite the linkage. When a spring is used, a single-acting pneumatic cylinder can be used as the pneumatic cylinder, which then only causes the opening of the valve. For closing the valve, the cylinder is switched to a driving pressure-free condition, and the spring, as a result of its tension force, pulls the valve back into the closed position. This has the advantages that a lower-cost pneumatic component can be used and that the contact pressure of the valve needle in the valve seat can be exactly predetermined by the spring.
In certain preferred embodiments of the invention, the valve, the pneumatic cylinder and the linkage—and optionally the spring—can be arranged to be standing side-by-side and are jointly applied to the lever. The side-by-side standing arrangement of the elements leads to a short height which is specifically advantageous when used in cryogenic environments.
In certain preferred embodiments of the invention, the pneumatic cylinder—and optionally the spring—stand on one side of the valve, while the linkage is arranged on the other side of the valve. During opening and closing movements, this results in a stepping-down because the valve is now arranged between the pneumatic cylinder and the linkage, so that a moving-out movement of the pneumatic cylinder results in a smaller opening movement in the valve. This stepping-down permits an extremely minute movement of the valve block in the valve seat and leads to a very exact proportioning.
The invention as well as additional details of the invention will be explained in detail in the following by means of an embodiment schematically illustrated in the figures.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.